1. Technical Field
The present invention relates to a method and system for supplying power to a processor in general and, in particular, to a method and system for providing a voltage to a processor within a computer system. Still more particularly, the present invention relates to a method and system for providing a tightly regulated core voltage to a processor within a computer system.
2. Description of the Prior Art
Many high-performance processors require two voltage levels for normal operations, one voltage level for operating processor I/O transistors and the other voltage level for operating processor core transistors. Typically, the operating voltage for the processor I/O transistors is directly supplied by a standard 3.3V power supply having a regulation of about .+-.5%. This results in a voltage range of as low as 3.135V and as high as 3.465V for the processor I/O transistors. The voltage for operating the processor core transistors, known as core voltage, may require a voltage of 2.7V with a tolerance of .+-.100 mV or better. Typically, this core voltage is also provided by the standard 3.3V power supply via a voltage regulator.
In order for a voltage regulator to function correctly, there needs to be at least a 0.5V difference between the input voltage and the output voltage of the voltage regulator. This 0.5V voltage differential is known as the "headroom" of the voltage regulator. In the meantime, the continued demand of processor performance levels to higher frequencies within a specific technology often requires a higher core voltage. As the core voltage goes up, there may not be enough "headroom" for the voltage regulator to function properly. One obvious solution to this problem would be to upgrade the power supply from a standard 3.3V to a standard 5.0V. But, needless to say, one of the many disadvantages of operating a 3.3V processor under a standard 5.0V power supply is that excessive electrical power is required to be dropped across the voltage regulator, resulting in power being wasted. Further, the wasted power, usually in the form of heat, also needs to be properly dissipated from the chassis of a computer system in which the processor is installed.
In addition, during the powering-up of some processors, the voltage difference between the processor I/O transistors' voltage and the core voltage must be maintained within a certain range of each other. If this voltage differential becomes too large, some transistors within the processor may get damaged or, at a minimum, the life of the processor will be unnecessarily shortened. In order to maintain compatibility with the standard 3.3V technology, it would be desirable to provide an improved method and system to provide a tightly regulated processor core voltage within a computer system such that a standard 3.3V power supply can still be utilized for the computer system having a processor with a higher core voltage demand.